The invention relates to vibration absorption and in particular to a controllable equipment mount (also referred to herein as a xe2x80x9ccontrollable mountxe2x80x9d or a xe2x80x9cmountxe2x80x9d) for isolating equipment from shock loads and small amplitude acoustic vibrations.
To minimize transmission of small amplitude vibrations into surrounding water, shipboard equipment and/or equipment platforms are often mounted on resilient mounts. The standard resilient mount stiffness must be sufficiently low to ensure adequate attenuation of input excitations. However, a mount with a sufficiently low stiffness to handle such excitations is not stiff enough to compensate for shock loads such as those experienced during battle conditions. Thus equipment mounted with a standard resilient mount would experience large deflections when subjected to shock loads. Accordingly, a mount is needed that attenuates vibrations for a wide range of loads.
Runge, U.S. Pat. No. 5,429,338, hereby incorporated by reference in a manner consistent with this invention and application, provides one solution to the problem of dealing with load variation. This patent discloses an equipment mount having three components, including a base mounted to a foundation, a retainer on which the equipment is mounted, and a resilient member disposed between the base and the retainer. The resilient member and the retainer are shaped to provide shock isolation over a large displacement range.
While the equipment mount of Runge provides significant improvements over previously known mounts, the range of stiffness is still somewhat limited so that different mounts may be necessary for different applications. Furthermore, the mount of Runge may be insufficient for supporting very large loads, or its footprint may have to be increased to support very large loads. Accordingly, a mount is needed that can adjust to a wider range of load variations to accommodate a wide variety of mount requirements. Furthermore, a need exists for supporting larger loads while maintaining a small footprint.
It is accordingly an object of the invention to provide a controllable mount having a variable internal pressure and volume.
A further object of the invention is to provide a mount that is tunable to a plurality of differing load conditions.
To achieve the foregoing objects, and in accordance with the purposes of the invention as embodied and broadly described herein, there is provided a controllable equipment mount for substantially isolating equipment from shock loads and acoustic vibrations. The controllable equipment mount comprises a base (or a xe2x80x9cbase platexe2x80x9d) for securing the controllable equipment mount to a foundation and a load plate positioned substantially parallel, and preferably parallel, to the base. The load plate is adapted for mounting equipment on it. The controllable equipment mount further comprises a C-mount section (or a xe2x80x9cconnecting mountxe2x80x9d) for connecting the load plate and the base, the C-mount section being secured to both the load plate and the base. The C-mount section is sealed between the base and the load plate by any suitable means, e.g., with O-rings, and is held in place by fasteners attaching it to the base and load plate. Thus, the C-mount section forms a closed chamber between the base and the load plate. A passageway is positioned in a wall of the chamber, for providing communication between the chamber and area outside the chamber. The passageway may be used to inject gas into the chamber to vary pressure in the chamber, thereby adjusting stiffness of the controllable equipment mount. In one embodiment, the passageway is provided in the load plate, e.g., an upper surface of the load plate.
In another aspect of the invention, a controllable equipment mount is provided for substantially isolating equipment from shock loads and acoustic vibrations. The controllable equipment mount comprises a base for securing the mount to a foundation, a load plate positioned substantially parallel, and preferably parallel, to the base, the load plate adapted for mounting the equipment, and a connecting mount for connecting the load plate and the base. The connecting mount is secured to both the load plate and the base and defines a closed chamber between the base and the load plate. The controllable equipment mount further comprises means for adjusting stiffness of the mount to enable the mount to be used with different loads and in a variety of environments. The means for adjusting stiffness of the mount may include a means of varying internal pressure within the chamber.
In yet another aspect of the invention, a controllable equipment mount is provided for substantially isolating equipment from shock loads and acoustic vibrations. The controllable equipment mount comprises a base for securing the mount to a foundation, a load plate positioned substantially parallel, and preferably parallel, to the base, the load plate adapted for mounting the equipment, and a first connecting mount for connecting the load plate and the base, the first connecting mount being secured to both the load plate and the base and defining a first closed chamber between the base and the load plate. The controllable equipment mount further comprises a second connecting mount, within the first connecting mount, the second connecting mount being secured to both the load plate and the base, the second connecting mount defining a second closed chamber between the base and the load plate. The controllable equipment mount further comprises pressure adjustment means for adjusting an internal pressure of at least one of said first and second chambers.
In any embodiment of the invention stiffness of the mount may be adjusted by varying pressure in the chamber of a single chamber mount, or in at least one chamber of a two chamber mount, applying a mechanical force, e.g., by using an electromagnetic augmentation unit (EAU), in the chamber of a single chamber mount or in at least one chamber of a two chamber mount, or by combining the variance of pressure and the application of a mechanical force in the chamber of a single chamber mount or in at least one chamber of the two chamber mount.
The invention is also directed to a method of adjusting stiffness of a controllable equipment mount used to substantially isolate equipment from shock loads and vibrations. The method can be used with any of the controllable equipment mounts of the invention. The method comprises adjusting the stiffness of the equipment mount by varying pressure in one or more chambers of the equipment mount, and/or by applying a mechanical force between the base plate and the load plate.
Pressure is varied by introducing a sufficient amount of gas into the chamber of a single chamber mount or into at least one chamber of a two chamber mount until a desired stiffness is achieved. Of course, if stiffness is excessive, gas can be released from the chamber or chambers. Any suitable gas may be used, such as air, argon, nitrogen, or carbon dioxide.
A mechanical force may be applied by providing an EAU in a single chamber mount or in at least one chamber of a two chamber mount. The EAU comprises an outer magnet assembly, an inner magnet assembly and a coil assembly. Application of electric current to the coil assembly creates a magnetic field in and around the coil assembly. The magnetic field causes a force to be applied to the load plate in a direction opposite to that of the load force, which increases stiffness of the equipment mount. In this manner, the mount is controlled to stiffen only when required for a particular application, thereby enabling the operator to operate the mount in a manner or mode that gives the mount an optimum acoustical attenuation for that particular application.
These and other features, objects, and advantages of the preferred embodiments will become apparent when the detailed description of the preferred embodiments is read in conjunction with the drawings attached hereto.